CONVOLVULACEAE 143 



passages Kerner describes the blossoms of Convolvulus, like those of Gentiana {c/. 

 p. 100), as * revolver flowers.' 



son. C. arvensis L. (Sprengel, 'Entd. Geh./ pp. 107-8; Herm. Muller, 

 'Fertilisation,' pp. 423-4, 'Weit. Beob.,' Ill, p. 6; Kirchner, 'Flora v. Stuttgart/ 

 pp. 548-9; Burgerstein, Ber. D. bot. Ges., Berlin, vii, 1889 ; Schulz, 'Beitrage,' II, 

 p. no; MacLeod, Bot. Jaarb. Dodonaea, Ghent, i, 1889, p. no, iii, 1891, p. 310, 

 V, 1893, pp. 328-9; Schilberszky, Bot. Centralbl., Cassel, Beiheft iii, 1893, pp. 447-8, 

 Bot. Centralbl., Cassel, Ixii, 1895, pp. 342-6, Ixiii, 1895, pp. 160-1; Loew, 'Bliiten- 

 biol. Floristik,' pp. 277-8; Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 106, 164, 

 'Weit. Beob. ii. Bl. u. Insekt. a. d. nordfr. Ins.,* p. 238, 'Bl. u. Insekt. a. Helgoland'; 

 Warnstorf, Verb. bot. Ver., Berlin, xxxviii, 1896.) The fragrant flowers of this 

 species close during bad weather and at night. Burgerstein says that at Vienna and 

 Prague they open from 7-9 a.m., closing again about 5 p.m. At Ruppin, according 

 to Warnstorf, they open 9-10 a.m., and close between 6 and 7 p.m. He describes 

 the pollen-grains as white in colour, ellipsoidal, delicately tuberculate, up to 88 fx. 

 long and 56/1 broad. 



Anthesis lasts a day. The funnel-shaped corolla is either reddish with five 

 longitudinal white streaks, or entirely white (var. hololeucus Knuth): its base is 

 yellow. Nectar is secreted by the orange-yellow base of the ovary, and covered 

 by the broadened lower ends of the filaments, leaving only five narrow nectar- 

 passages. Where the filaments touch they are closely beset with small stiff 

 projections, preventing the passage of an insect's proboscis, which must be inserted 

 into one of the five narrow passages in order to reach the nectar. As the 

 stamens surround the style and their anthers dehisce extrorsely, the latter must 

 be touched by any large insect sucking nectar, and as the two stigmatic branches 

 project beyond the stamens, and spread out their papillose inner surfaces above 

 them, these must necessarily first come into contact with visitors. The first 

 flower visited by an insect will be self-pollinated as its visitor withdraws, while 

 the second will be crossed. Should insect-visits fail, automatic self-pollination 

 can take place towards the end of anthesis when the flower bends down and 

 the corolla drops, so that pollen falls upon the stigma. And it may also be 

 effected in a still vigorous upright flower by elongation of a stamen till its anther 

 is applied to the stigma. 



There are various forms of blossom. At Stuttgart, for example, Kirchner 

 observed a small-flowered autumn form, with stamens so short that the yellowish- 

 brown anthers were almost sessile. These remained sterile, for there were scarcely 

 any insect-visits, and the anthers were too far from the stigma to render autogamy 

 possible. Schilberszky noticed the same form at Buda-Pesth, with numerous 

 transitions to female flowers. Besides this arrested form, produced by the action 

 of a fungus, Burgerstein observed two others at Vienna and Prague, one with 

 a large corolla, long stamens and violet anthers, and the other with a corolla of 

 medium size, shorter stamens, and white anthers. 



Schulz describes two forms differing in their mechanism. One of these is 

 small-flowered, chiefly visited by bees, and homogamous or slightly protogynous, 

 its stigmatic branches interlocking with the pollen-covered anthers, so as to make 



